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Tre e C a re A d v i s o r N ew s l e t t e r http://

Dave Hanson and Gary Johnson, Managing Editors

Inside This Issue:

Volume 11 Number 2

Spring has Sprung!

Need a “small” Tree? By Dave Hanson

1 I’ll get you started on page 5. Check out “who” arrived in the TCA program and

Quick Hits / Volunteer Opps By Dave Hanson


Putting Down Roots: By Cliff Johnson

3 Spring also brings a moment of reprieve to our trees - at least it should. During

Please Welcome,


Linda Guertler - one of the spring arrivals to the TCA program provides a pretty good look at the benefits of fungi on page 6…

TCA Class of 2004 Tree Friendly Fungi By Linda Guertler

look at where they are taking the TCA message…

the spring months, give the trees a break. Put your time and energy into pruning the grass and quit pruning the trees for a little while. Give them a rest while they leaf out… See the article on page 11 regarding the “whys” of tree pruning or at


least some of them... Are you still with me? Now you can go back and read the other articles that have

Arbor Day, Involvement By Betsy Mcdonough


Why? Pruning Trees By Dave Hanson

11 standby called buckthorn to a new and potentially lethal (to ash species) bug called

Emerald Ash Borer (EAB) News from Sue Burks, MnDNR

17 And remember - it’s Oak Wilt Season...



been included in this newsletter… Those exotics are still with us from a good old the Emerald ash borer…

Need a “small” Tree? The family Rosaceae covers a number of Minnesota’s native trees and shrubs. Members of the family include the cherries, apples, hawthorns and the juneberries, to name a few. However, it is one of the other family members that is the focus of this article. The American “Rowan” tree, like many of us, finds solitude in the cool northern forests of North America. One of the regions where it grows best is in the northern great lakes region. This small stature tree, especially its cousins, has become popular as an ornamental in the northern states due to its finely toothed compound leaves, flower clusters and sometimes persistent fruit. Continued on Page 19

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Quick Hits The TCAAG has added several new members and is currently considering a new name. TCAAG just doesn’t flow and roll off of one’s tongue… So, if you have an idea for a new acronym or a project for the TCAAG to work on - let us know. We will be getting together again on Thursday, July 29th at 6:00 pm. Or bring your ideas to the meeting in Green Hall room 116A on the Saint Paul Campus.

WWW.MNTCA.ORG Gearing up for the new season! There are some volunteer opportunities listed on the website. The planting season is upon us!

There is also a good deal of valuable information under “Resources and References.” I have been slowly expanding the “TCA Tree Identification” pages and “Notes From the Field.” Remember this website is for TCAs ! Let me know what you would like out there!

Again, there are opportunities to help out with various activities on campus with the TRE nursery. Typically these opportunities are research related Help some kids plant a tree! It can be fun and rewarding! Photo: Dave Hanson

but can be rather messy and the work is far from glamorous.

A “Contact Tree” It is my understanding that there was good response to the request for a “Phone Tree” and there are a good number of contacts out there. As I updated the directory for 2004, I flagged the “Contact” TCAs with an asterisk (*) behind their names. As of yet, this method of contacting people has not been used, but if you need to reach the people in your area for a planting event or speaking engagement that needs an audience or a speaker for that matter - let’s give it a whirl.

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Putting Down Roots - A column in the Chaska Herald. By Cliff Johnson, Carver/

time this summer -- small

20 years earlier. Some of

Scott Master Gardener

black berries.

the trees and shrubs at

Glossy green leaves in late fall spell trouble Everyone loves to

I liked the tree a lot until I discovered the

have become overgrown

berries. When eaten by

and unsightly. I was in-

look at colorful fall leaves. birds, these berries are In a few months, we’ll marvel at the reds, yel-

this site, unfortunately,

vited to the site to offer

spread across my yard and advice on pruning and genthe surrounding neighbor- eral tree and shrub main-

lows, oranges and scarlets. hood and the seeds sprout tenance. A dozen of the This fall, train your into seedlings that will not woody plants in this land-

become attractive fernleaf scape are buckthorns -- a popular landscape plant leaves on small trees after buckthorns. Rather, the two decades ago. Native all the red, yellow, orange seedlings revert to the non-native, invasive parent to Europe, buckthorn was and scarlet leaves have eyes to search for green

cascaded from the tree branches. The green

buckthorn species. Removing my at-

leaves you see still clinging tractive ornamental buckto branches in late Octo-

thorn was a lot of work

ber and early November

but the tree had to go. I

imported to North America in the late 1700s and widely planted as hedging

Rhamnus cathartica - terminal thorn and “hoof” like buds of a buck - hence the common name buckthorn. Photo: Dave Hanson

material until 1930. Ornamental varieties of buck-

after all the colorful leaves can’t very well go on writ- thorn (like my fernleaf vahave fallen are buckthorn. ing with a clear conscience riety) continued to be sold

Mature leaves in August. Note the veination pattern refered to as arcuate veination - arcing

and planted right up until

from the leaf base to the apex.

tion when I have a source

the last few years. The

Photo: Dave Hanson

from a very handsome

of the problem growing in buckthorns on this Waconia lot were full of beautimy yard. My tree was

nine-year-old fernleaf

okay as long as it didn’t

ful 1/4-inch diameter ber-

plenifolia) that was planted

produce berries but, given ries. And, you guessed it, tiny buckthorn seedlings the plant’s propensity to

right outside my office

propagate from seed, it

are popping up every-

A weeks ago, I spent a half day removing and digging out the roots

buckthorn (Rhamnus as-

about buckthorn eradica-

window in 1993 by a land- was time to reach for the saw and shovel. scape contractor. It had grown to about 15 feet and, as the name implies, sported very attractive fern-like leaves. It also produced -- for the first

Later in the same week, I made a house call

where. I’ve written about buckthorn before, and perhaps you wish I’d find a

at a home on Lake Waco- new topic, but buckthorn nia where a beautiful land- is a serious problem in scape had been established Minnesota yards and

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Putting Down Roots... wooded areas and each of at the glossy, green-leafed

have published helpful

us can play a part in pre-

guidelines for fighting this

plant this fall after the

venting a total takeover by other leaves have fallen. this invasive plant. You may have

invasive plant. Eradication

Mary Lerman, hor- procedures and close-up photos of the leaves and ticulturist with the Min-

heard the term allelopathy. neapolis Park and Recrea-

berries can be viewed on

It refers to suppressive

tion Board, says the

dozens of internet sites.

effect of one plant on an-

woodlands and wetlands in

In some areas,

other through production Minneapolis are infested

homeowners and other

and release of natural

volunteers have joined

with common buckthorn.

compounds. Black walnuts “One only needs to drive

forces to eradicate buck-

possess allelopathy. To-

along Minnehaha Parkway, thorn from entire

matoes and peppers and

the River Road parkways,

neighborhoods. Perhaps

some other plants will not through Theodore Wirth

you are just the person to

grow in soil where black

Park and along Diamond

begin a buckthorn removal

New emerging leaves - April 29

walnut roots are present.

Lake to see its devasta-

campaign in your

Photo: Dave Hanson

Sunflower seeds also cause tion,” she says. Some exthis phenomenon. There

perts have written that, if

are no plants growing un-

buckthorn isn’t removed

piece. By the way, my

der my bird feeders.

soon, future generations

buckthorn removal project

Buckthorn puts all the pieces together for

root fungi, a long growing season, hungry birds that

Photo: Dave Hanson

center and bought a small but very attractive blue-

Buckthorn eradica- needle Japanese white pine tion is complicated and

and planted it where the

spread the seeds, no natu- labor intensive. If you

fernleaf buckthorn grew

ral predators and an allelo- have buckthorn present

for nine years. I should

pathic effect on other

on your property, I en-

have planted the pine in


courage you to begin the

the first place.

The first step in ries

Okay, I’ve said my

will not have the opportu- had a happy ending. I nity to enjoy the flora and drove to a local garden

total takeover: A vigorous fauna of woodlands and root system, mycorrhizal wetlands.

Late September leaves and ber-


controlling the spread of

process of eliminating it. The Minnesota Depart-

buckthorn is identification. ment of Agriculture and the University of MinneThat’s why I hope you’ll stop and take a close look sota Extension Service

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Please Welcome “The TCA class of 2004.” At the beginning of February, I was a little concerned that we would have to cancel this years TCA core course due to lack of participants… Well with a little flexibility on our part and some last minute calls and requests to the regional offices – we filled to capacity and added a few extras. Yes, extras; two urban forestry students from the University of Minnesota and a Regional Extension Educator from south-central Minnesota (my old stomping grounds). Saint Paul Course

Lamberton Course


Instructor: Gary Wyatt

Gary Johnson Dave Hanson

Regional Extension Educator Mankato Regional Center

Charles Krueger Diane Richards Gary Wyatt Thomas Dunlap Nori James Diane Booth Daniel Baltes Kathleen Bonnett Janet Erdman Linda Guertler Keith Dougherty Rebecca Bandelin Ada Hegion Beth Storey Barbara Whipple Michael Oslund Shannon Lloyd Norman Erickson Mary Laine Jan Morlock Louise Levy Cynthia Hammel Holly Johnson Ron Pierce Winnie Williams

County Anoka Blue Earth Blue Earth Carver Carver Cook Dakota Dakota Dakota Dakota Douglas Dunn, WI Hennepin Hennepin Hennepin Isanti Nicollet Olmsted Ramsey Ramsey St. Louis Washington Washington Washington Washington

County Judy Harder Steve Harder John Jirak Dorinda Speh Patricia White Marcy Bode Charles Nordby Laurie Iverson Mark Rose Kristi Megli Robert Welker

Cottonwood Cottonwood Le Sueur Murray Murray Nicollet (Brown) Redwood Redwood Redwood Sibley Yellow Medicine

Northeast to Yellow Medicine on the west edge - The TCA program is getting around.

Photo of the Lamberton crew...

As you can see members of this class have come from all four corners of Minnesota and they are truly taking the TCA message farther than it has gone before. To me this is really exciting – it doesn’t matter what size the community is in Minnesota – there needs to be a voice for the trees and TCAs are it! Thanks for getting out there and speaking on behalf of the trees…

From Cook County in the

Dave Hanson

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Tree Friendly Fungi and Bacteria Linda Guertler Dakota County TCA, University of Minnesota, MS of Ag in Horticulture Graduate Student Not All Fungi and Bacteria are Bad!

For many people, the news that their prized tree is loaded with thousands of fungi and bacteria would likely be distressing. You might be surprised to learn that most microorganisms growing on or near trees, such as fungi or bacteria, are not harmful to the tree and may in fact be quite beneficial. The relationship is similar to that of the human body, which Below: The Beetles of DED and constantly harbors thousands of fungi and bacteria. Some even improve the functioning of an Elm showing early “flagging.” certain activities, such as the bacteria that live within the intestinal tract where they aid in digestion and produce Vitamin K. In addition, for both trees and the human body, health can be more easily maintained when colonized by the “good guys” because it makes it harder for the “bad guys” to get established and cause disease. When the environment is changed so that optimum growing conditions are altered, this balance may be disrupted. Trees (like people) under stress have less disease resistance and may become vulnerable to harmful fungi or bacteria. The Bad Guys With all the publicity given to the disease causing fungi and bacteria, it is no wonder people are unaware of the good things these microorganisms can do. Just say the words “Dutch elm disease” and “Oak wilt” and a look of sadness or worry is likely to be the response. Common Fungal Diseases •

the northeastern United States. It is a fungal disease that is spread overland by beetles that pick up fungal spores when they feed on the sap of infected trees and then move on to infect healthy trees. It also spreads below ground through roots that intermingle with the roots of neighboring elm trees. When the tree detects the presence of the fungus infection, it attempts to prevent its spread by clogging up the water conducting vessels. Unfortunately, this process also deprives the tree of water. Leaves quickly begin to wilt, then turn yellow and brown, and eventually branches and the entire tree dies as the disease continues to spread.

Below: An Oak killed by oak wilt and some of the beetles responsible for overland transmission.

Dutch elm disease has had a devastating impact on the American elm throughout

Oak Wilt is another fungal disease that is wiping out great numbers of oaks in the eastern part of the United States, especially the Upper Midwest, including central Minnesota. The fungus that is responsible for oak wilt is different than the one that causes Dutch elm disease, but it is spread in a similar manner. The predominant means of transmission is through root systems that graft with each other, but it can also be spread overland by sap beetles. The beetles are attracted to the spore bearing mats produced on trees that have been killed by oak wilt and they then fly on to feed on the sap from fresh wounds of healthy oaks and contaminate them with the spores stuck to their bodies. As in Dutch elm disease, the infection process triggers a response in the tree that causes the vascular system to plug up and stop the flow of water. Leaves rapidly wilt, turn color and die around the outer margins and from the top of the tree

Tree Friendly Fungi and Bacteria

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crown downward. The red oak group is more susceptible than the white, but either can get oak wilt. Red oaks can be killed within three weeks after infection, while white oaks can take several years to die. Common Bacterial Diseases •

Fire blight is a bacterial disease of plants in the rose family, including apple, crabapple and mountain ash. Infections are typically spread from tree to tree by bees feeding on flowers. Very rapid death of tissue results, causing branches or the entire tree to look like it has been scorched by fire within a short time frame. Infections result in the development of cankers and death of branches or the entire tree.

Bees and Fireblight

Crown gall is a disease caused by a bacterium that lives in the soil and when it infects a tree it causes the tree to form tumor-like galls on the roots and stem. Although the galls can become quite large and grotesque, they typically only cause stunting, make the tree more susceptible to drought damage, winter injury and infections from other organisms. Unless the gall completely girdles the stem a tree is rarely killed.

What Do The Good Ones Do? •

Mycorrhizae are the home run hitters in the world of beneficial tree fungus associations. Mycorrhizae, meaning “fungus-root,” are formed when one of the many different fungi that grow naturally and abundantly in native soils hook up with tree feeder roots in a mutually beneficial way. The fungus spreads out by tiny growth filaments called hyphae that penetrate either between or into the cells of the tree roots. This joint association is called mycorrhizae. The fungus benefits from the relationship by getting carbohydrates (energy) from the tree. The fungus decomposes organic matter, causing nutrients to be released. The tree benefits from the mycorrhizae by the fungus being able to grow more widely and deeper into the soil than the tree roots can, increasing the trees access to moisture and nutrients, including phosphorous, nitrogen, and copper. Some protection from disease invasions also occurs because of the protective covering the fungus provides over the tree root. Trees that don’t have mycorrhizae can survive, but most healthy plants have them and typically perform better when they do, especially if they are growing in poor soils. They usually have larger roots, grow more quickly, and are more tolerant of stress.

Crown Gall...

Soil fungi and bacteria associated with trees: Improve soil fertility by digesting and releasing nutrients from organic matter (nutrient cycling);

Hyphae (small projections into

Improve soil tilth by causing soil particles to stick together in aggregates;

tips greatly increase the absorp-

Control many harmful microorganisms by attacking them directly or preventing their establishment in the tree because the good guys were their first, and;

tion area of the root tip.

Release nitrogen from organic matter or directly from the atmosphere into a form that can be used by trees.

the soil) of Mycorrhizae on root

Myco means fungus Rhiza refers to roots.

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Tree Friendly Fungi and Bacteria •

Fungi and bacteria on leaves, flowers and other plant parts benefit the tree by fighting off disease causing organisms. If a tree has numerous types of harmless bacteria or fungi that have taken up residence, when a harmful new type tries to move in it has a more difficult time getting established.

How to Keep the Good Guys Around To keep beneficial fungi and bacteria thriving and in tip top shape, it is particularly important to maintain the health of the soil where the tree is growing. Healthy soil will be best maintained if you or anyone you contract with to do work for you follows these rules: Do’s •

Do maintain a layer of organic matter on the soil surface (e.g. wood chips, plant debris or compost). This is a source of food for soil microorganisms and necessary for their survival. It also helps avoid compacting soil and keeps the soil moist longer.

Don’ts •

Don’t scrape off the surface layer of topsoil

Don’t compact the soil. Soil compacted from activities like operating heavy equipment or piling heavy objects over tree roots deprives tree roots and beneficial organisms of essential oxygen.

Don’t mix up soil layers or dump large quantities of soil from another site.

Don’t use soil fungicides or sterilizers.

Don’t dispose of chemicals, petroleum or other toxic materials or construction supplies on or bury in soil.

What if I did some of those bad things? Okay, so you don’t have the best soil and wonder if there is anything you can do to improve the situation and reintroduce friendly fungi and bacteria to the tree’s growing environment. Yes! •

Apply a surface mulch of organic matter. Fungi and bacteria thrive under different conditions, so the type of material you apply will influence the balance of each that you have. Bacteria will be more prevalent in fresh green materials, such as grass clippings, or moist (not wet) compost that has been turned frequently (turning breaks up the “webbing” fungi create when growing). To create a bacteria dominated compost, mix together: 25% high nitrogen material (manure or spring grass clippings) 45% green material ( any green plants, kitchen scraps or coffee grounds) 30% woody material (wood chips, sawdust, shredded newspaper) Fungi will predominate in drier organic matter (less than 40% moisture) with less green material (or none, like wood chips) or compost that has not been turned very often.

Spore inoculations of the fungal portion of mycorrhizae can be purchased for application in soils, but under most circumstances they are not necessary. For a quick introduction

Tree Friendly Fungi and Bacteria of fungal spores when planting a new tree after digging the hole, mix in some native soil and compost to the soil before backfilling the hole. Fungal spores will likely be present in native soil, and compost will help create an environment they can survive in. Even if you don’t add native soil or purchase an inoculum of fungal spores, the spores of fungi that form mycorrhizae float ubiquitously in the air so they will become reestablished in time if soil conditions are right. So, add that compost! •

Whether applying wood chip mulch, compost, or any other organic matter, don’t ever apply organic matter that smells bad or has an alcohol odor. Alcohol is produced when organic matter has not been well aerated and is toxic to plants in very small quantities. If you detect a bad smell, mix up the material frequently to introduce air and wait for the smell to go away before application.

A Final Word Keeping healthy populations of tree friendly fungi and bacteria is a good thing! Providing the conditions they need to be healthy and thriving, will help your trees remain healthy too. For More Information Agrios, George N. 1997. Plant Pathology, 4th Edition. Academic Press. San Diego, CA. Baker, Christine. 2002. Iowa State Extension Service – Extension News. Fungal Friends. Found at Brady, Nyle C and Ray R. Weil. 2000. Elements of the Nature and Properties of Soils. Prentice Hall, Inc. Upper Saddle River, NJ. Haugen, Linda. 1998. USDA Forest Service. How to Identify and Manage Dutch Elm Disease. Hoitink, H., M. Drause and A. Stone. 2000. Disease Control Induced by Compost in Container Culture and Ground Beds. Ohio State University Extension Circular 177-01 found at http:// Ingham, Elaine. Brewing Compost Tea. Fine Gardening. Accessed 4-16-04 at http:// Jackson, Eric. 2004. When a fungus is a good thing. Science. Vol. 9 #24 found at http:// O’Brien, Joseph and Manfred E. Mielke, Dale Starkey, and Jennifer Juzwik. USDA Forest Service. How to Identify, Prevent, and Control Oak Wilt. pubs/howtos/ht_oakwilt/toc.htm Podila, Godi. 2000. MTU News. 4/24/00 found at genes.html Rockwood, Larry. George Mason University. Mutualism course sheet found at http:// Sinclair, Wayne A., Howard H. Lyon and Warren T. Johnson. 1987. Diseases of Trees and Shrubs. Cornell University Press. Ithaca, NY. Shigo, Alex L. Some Tree Myths Corrected. Tree Trust for Haringay website accessed 1/04 found at University of Minnesota Extension Service. 2000. Bulletin BU-07403 Soil Manager. Website ac-

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Tree Friendly Fungi and Bacteria cessed 4-16-04 Vaneste, J.L. 1996. Honey gees and epiphytic bacteria to control fire blight. Biocontrol News and Information. Vol 17. No. 467N-78N. found at Photos All photos except those otherwise noted - Keslick and Sons Technical Tree Biology Dictionary found at Crown gall photo – Wayne’s World. To Be or Not to Be a Gall. Website http:// Dutch elm disease photos - Haugen, Linda. 1998. USDA Forest Service. How to Identify and Manage Dutch Elm Disease. ht_ded.htm Oak Wilt photos - O’Brien, Joseph and Manfred E. Mielke, Dale Starkey, and Jennifer Juzwik. USDA Forest Service. How to Identify, Prevent, and Control Oak Wilt.

Arbor Day - Involvement Grows In honor of Arbor Day, the City of Oakdale holds an annual tree giveaway for their residents. Yesterday, April 24, TCAs Jane Kline, Diane Crea and Betsy McDonough along with our new Washington County Master Gardener intern, Lynn Barnum, assisted in the giveaway. While the city has done this for a number of years, this is the second year that a number of TCAs, other than Jane (City's Tree Board member), have been involved. Last year we played a slightly more passive role in that we were there to answer questions IF people had them. As we watched a number of trees leaving with homeowners that clearly needed some pruning, we saw an opportunity to get more actively involved and provide a greater service in the future. So this year was a different story. There were a total of 300 bareroot trees - Red Splendor Crabs and Northwood's Maples. Due to our fabulous training and knowledge about proper planting depth and the consequences of nurseries sometimes planting too deep, we decided we needed to inspect all trees before they were planted AND give planting instructions to the homeowners. So, we formed a line and as each homeowner received their tree they brought them to the TCAs, armed with pruners and red markers. We saw some incredible root structures! As we were pruning away the multitude of advantageous roots, figure 8's, and potential stem girdling roots, we had the opportunity to talk with each homeowner and tell them how to correctly plant and care for their tree. This was a great opportunity to get involved with the community, have direct one-on-one contact and educate a lot of people. People were very willing to wait in line for their turn. They were curious, appreciative, and wanted to gain the knowledge and understanding so they could care for their trees properly. All in all - a great day. Thanks to Jane Kline for getting TCAs involved. Respectfully submitted, Betsy McDonough


Why do we prune trees?

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By Dave Hanson Many of us have had the pleasant (?) experience of the tag-along-toddler with only one question on their little mind, “Why?” While this repeated inquiry can be, shall we be polite and say, challenging! We understand that the tag-along-toddler is learning and cataloging some tidbits for later. Whether people are listening to a speaker or reading an article – the topic of pruning reduces many of us to the tag-along-toddler phase of our lives with one burning question “why?” This article will repeatedly ask that question and hopefully provide some answers besides, “because!” Let’s get started with this comment: Trees in a “natural” forest are seldom pruned and they do fine. On the other hand people in urban areas insist on pruning trees frequently… Why? Are urbanites simply “control freaks” with a need to control some living thing? Not exactly, there are valid reasons (safety, health of the tree, and aesthetics) to get out there and take a good look at the structure and condition of the trees in our landscape. Trees in the natural forest for example tend to randomly drop limbs (natural pruning) and fall over unpredictably during storm events or from internal decay. Increased potential for property damage and personal injury in the urban forest dictates that limb dropping and trees falling over should be predicted and controlled, as much as possible. Any tree may develop structural problems or become damaged in such a way that it presents a risk. So, developing a regular inspection and pruning cycle for landscape trees is highly recommended to help eliminate some of the “risk.”

Bad decisions leading to more bad decisions: You cannot correct the decision to leave this

Many consulting arborists are trained to identify those “risks” in trees and can make recommendations to eliminate or reduce the risk to an acceptable level. Often reducing the risk can be accomplished without removing the tree by utilizing one of the following approaches:

tree during construction by pruning it excessively to raise the crown and to “move” it away from the building. Photo: Dave Hanson

Three basic approaches to pruning: From the United States Forest Service brochure “How To Prune Trees” (Bedker et al.): 1) Crown reduction: A method to reduce the overall height of a tree. Why? Most often put into practice under power lines to alleviate line conflicts. According to a flyer from Connexus energy (Spring 2004) – “Trees are the number one cause of power outages.” This approach may also be employed to clear site lines for a scenic overlook or vista.

Power line clearance. Photo by Chad Giblin, U of M.

Page 12

Why? Crown reduction or drop-crotch pruning is not topping; yet, it should be considered as a last resort treatment. Why? Crown reduction opens multiple large and small wounds on a tree and those wounds can be entry points for insects or disease‌ 2) Crown thinning / cleaning: This technique is often used to open up the canopy for air movement through the tree and to provide light penetration to the understory. Beyond that, this pruning approach considers many things: correction of structural problems such as: tight branch angles, included bark, crossing branches, broken or split tree parts‌ Why? Correcting structural problems can prevent problems from loading events (wind, ice, or snow) or simply the weight of a maturing limb. Consider a limb or branch to be a lever arm that you learned about in physics – if you load that lever arm and it is not firmly attached to the tree or was previously damaged it is likely to fail.

Co-dominant leader split out by

Crown cleaning also consists of removing deadwood, hangers (broken branches) as well as removal of diseased wood or insect infestations.

snow load.


Photo by Josh Plunkett, U of M.

Deadwood and hangers (lodged, detached branches) present a risk to people, cars, houses and other objects (targets) below. Also, by removing signs of disease and / or insect infestations a serious problem for the tree may be stopped before it progresses to a full blown disorder. Maintenance and correction of storm damage fall into this category. 3) Crown raising: Simply put, this is the removal of lower branches to improve site lines near roads and to allow for movement of people and equipment under trees. Along city streets for example, many municipalities remove permanent tree branches to a minimum height of 16 feet from the ground or street surface. Why? Garbage trucks and other big rigs will prune the limbs by tearing them from the tree often causing irreparable damage to the main stem.

This hackberry stem was ruptured by a delivery truck hitting

Along sidewalks, permanent tree branches should be a minimum of 8 feet above the sidewalk to allow for pedestrian traffic and snow removal equipment.

a low hanging limb - see page 13 Photo: Dave Hanson

Depending where a tree is located in the landscape determines if branches are

Page 13

Why? raised or allowed to sweep to the ground. Why? Low hanging tree branches restrict movement and present poking and head-banging hazards in our yards and parks. So, in some instances the tree branches should be raised to allow people and equipment to move underneath Putting this into Practice: So, with those approaches outlined here’s a prediction – If you are responsible for a landscape that contains trees – there is some pruning in your future…or there should be!

But hold on, before you grab the chainsaw, consider taking a brief course on pruning or at least read some of the current research on pruning trees. Unfortunately, there are still a The low hackberry limb that was lot of incorrect pruning practices taking place – bad pruning cuts, pruning practices that struck by a truck. See picture permanently damage trees and pruning performed during the wrong season for the tree. Flush cutting:

on page 12 for resulting damage to the main stem…

There is a three cut method to pruning: cut number 1 is an undercut of the branch to pre- Photo: Dave Hanson vent the bark and wood fibers tearing down the main stem. Cut number 2 simply removes the weight of the branch outside of cut number 1. The third and final cut removes the branch stub near, but outside of the branch collar. However, a person can still find literature that describes the final pruning cut as follows: “Then cut the remaining stub flush and parallel to the main trunk” That is an exact quote from a currently available publication copyrighted in 1980. That description of the final cut is completely wrong! Why? The final pruning cut should take into consideration the branch bark ridge and the branch collar. Simplistically, the branch collar is a zone of fast growth and within this zone there are several protection mechanisms that protect the trunk of the tree from decay organisms that may enter the branch. By leaving the branch collar intact – the main trunk of the tree will be better protected from decay processes… A pruning cut that is “flush and parallel to the main trunk” leaves a large oval wound in the trunk tissue that a tree will have a difficult time sealing over with callus material. Protection zones and mechanisms are compromised and the tree is more likely to decay.

Top: Branch collar Bottom: Proper pruning cut vs.

Topping and Tipping: There are still companies topping trees and tipping branches on trees. There are still

flush cut Photos: Gary Johnson

Page 14

Why? homeowners requesting that trees be topped and that branches be tipped. Both topping and tipping are harmful practices to trees… Why? Topping and tipping are pruning cuts made indiscriminately on limbs with no regard for placing the cuts near protection zones. These cuts almost always result in rapid decay of the remaining portion of the limb, while at the same time stimulating large amounts of new growth in the form of epicormic branches, also known as water sprouts. The new growth is typically poorly attached and begins to add considerable weight to a limb or branch being weakened by decay.

Tree topping to allow would be

When to Prune:

shoppers to see store front

How about the perennial question, when is the “best” time to prune a tree? Let’s turn that question around – when is the “worst” time to prune a tree? From the trees point of view the months of April, May and into June may be the worst time to prune.

signage.. Photo by Patrick Weicherding

Why? First, this is the time of year when trees deplete their energy reserves and put most of it into new leaves. Pruning at this time places the energy that has been moved into branches, twigs and leaves onto the burn pile or into a landfill. This practice places the tree in a stressed state, with an energy deficit that may not be completely recovered in that season. Secondly, this is an active time of year for many disease and fungal pathogens (Oak wilt for example). The warm spring months of April, May, and June typically bring high humidity from spring rains, these factors provide an ideal environment for many pathogens to flourish. So, you have the environment for a pathogen, you have a pathogen – now, to complete the “disease triangle” there has to be a host! How about that tree in your front yard that was just pruned, it is probably a good host for some pathogen. So, yes, spring can be a bad time to prune… Another “bad” time to prune is late autumn into early winter... “Worst” time to prune - during the period of spring flower and bud break through leaf set in the early summer. Blossom on leatherwood…

Why? Pruning in late autumn and early winter can lead to winter injury. The pruning wounds may not have time to “harden off” or prepare for winter. This can lead to deeper freezing in the tissues around the wound and in essence a larger wound can be created that the tree will have difficulty dealing with.

Photo: Dave Hanson

So that leaves us with the summer months and late winter (dormant season pruning). Typically late winter or dormant season pruning is the “best” time to prune.

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Why? Why? During the late winter months (February and March), harmful pathogens are at a minimum, mostly inactive; therefore, this is a safe pruning environment from that standpoint. During this season, deciduous trees have hardened off and when the growing season begins the wounds will be sealed and the callusing process will begin. Final Thoughts: This brings us to another big question, should a homeowner hire a professional arborist to do the tree work or get out there and do it by themselves? Keep this though in mind; the balance of a tree or a tree limb can be difficult to judge. While, the task at hand may appear simple, tree work is a very dangerous profession.

What or Who is an arborist? For more information visit

One simple rule: If there is a power line nearby – consult with an arborist. Why? Power lines and in-experienced, untrained workers do not mix! At a minimum call the power company to discuss options… You may be able to schedule a line drop for a few hours. It is easier to physically disconnect and drop the line than to replace connections and repair damage after the tree falls the wrong way…assuming, you survive the incident and are able to repair the damage. Some basic guidelines: If the job requires a ladder, a consultation with an arborist may be in order. Why? By working from a ladder with a hand saw, chainsaw or even a pole pruner much of the necessary pruning cannot be accomplished and often the tree will end up be “lion’s tailed.” Lion’s-tailing leaves a tree with a reduced canopy, thus reducing its ability to photosynthesize. Arborists on the other hand will enter the tree with climbing gear (rope and saddle – NOT SPIKES) and or use a boom truck with a bucket to reach the tree top and branch ends. If you think the job requires a chainsaw, consulting an arborist is recommended. Why? Chainsaws are tools for trained, experienced hands. Untrained operators often do more harm than good to both the tree and the operator. Most of the pruning that a tree needs can and should be accomplished with a “hand” pruner or pruning saw.

Pruning disaster - a homeowner, power lines, a ladder, and a chainsaw… Photo: Dave Hanson

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Why? Exception: Yes, commercial / municipal arborists and tree-workers are trained in the use of chainsaws and will use chainsaws to complete a portion of their work. However, note that they also carry handsaws and use them appropriately. If you have storm damaged trees, consult an arborist and the tree may be able to stay in the landscape, safely for years to come. Why? Trees that have suffered structural damage from storms or accidents will not “recover” or “heal” in the sense that our bodies will heal. Thus, arborists are trained to understand the structure of a tree and to understand how a damaged tree will respond to treatments. If possible cabling, bolting and bracing may be part of that treatment. But, most importantly an arborist can answer the question – “Can this tree safely remain in the landscape?” If you are planning a landscape, please consult an arborist or a landscape designer. Why? It is important to select the right trees for your locations. Putting the right trees in the right places can dramatically reduce the costs of pruning and maintenance in your landscape. The bottom line is that feeling the need to prune trees does not make urbanites “control freaks”; rather, living in geographically condensed spaces in close proximity to mature trees renders us and our belongings potential targets to falling tree parts. Thus, out of necessity we need to care for our trees not only so that they are pleasing to look at, but so that they remain healthy, safe features in our landscape. Why? Because!

Mature Bur Oak… Photo: Dave Hanson

Works Cited: Bedker, Peter J., O’Brien, Joseph G., Mielke, Manfred E., How To Prune Trees. United States Department of Agriculture, Forest Service Publication NA-FR01-95

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Emerald Ash Borer DNR NEWS Indiana Department of Natural Resources 402 W. Washington St. W255 B Indianapolis, IN 46204-2748 For immediate release: April 22, 2004 Emerald ash borer confirmed in Indiana:DNR begins steps to contain spread. After receiving lab results from the U.S. Department of Agriculture, Department of Natural Resources officials confirmed that the emerald ash borer had infected a tree in Steuben County. This is the first confirmation of the ash tree-killing pest in Indiana.

Photo: Howard Russell, MSU Above - Size of the adult insect Below - The damaging larva

The ash tree-eating pest was discovered Monday at the Yogi Bear Jellystone campground on Barton Lake in Steuben County about 40 miles north of Fort Wayne. The adult emerald ash borer is slender with a bright metallic coppery green color. It is about one-third of an inch long. The larval, or immature stage of the insect destroys live ash trees by eating the layers under the bark of the tree that supplies nutrients. After those layers are destroyed, the tree starves to death within a short time. Infestations are most easily identified by tiny D-shaped holes that are visible on the tree's bark. The bark may also develop lengthwise cracks or fissures.

The adult insects D-shaped exit hole

To date, millions of ash trees have fallen prey to the emerald ash borer and a number of Michigan counties are under quarantine. The pest also has been found a few miles east of the Indiana border near Hicksville, Ohio and a few miles to the north in Quincy, Mich.

Photo: Deborah McCullough, MSU

State Entomologist Dr. Robert Waltz announced today that the state would begin to take steps to contain the spread of the infestation. The first step will be a survey of the infected area. The survey will determine, first, the number of ash trees that could serve as a host for the pest. Second, the survey will determine the extent of the infestation. Both of these steps are in preparation for trapping the emerald ash borer and the removal of all ash trees within a halfmile radius of the infestation.

Bark fissure on green ash Photo: James W. Smith

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Emerald Ash Borer Further, Waltz announced the DNR is placing a quarantine on Jamestown Township in Steuben County. The quarantine will forbid the transportation out of the township of any ash tree, including nursery stock, any ash logs or untreated lumber with the bark attached, and composted or un-composted ash chips or bark chips one inch or larger. Lastly, no cut firewood from any species of tree grown in Jamestown Township may be taken out of the township.

Photo: James W Smith.

DNR was first notified of a possible infestation by a local Purdue Extension educator. A DNR field entomologist responded and confirmed an infestation but was unable to confirm the presence of the emerald ash borer.

Ash tree in decline

Another DNR entomologist and a representative of the USDA's Animal and Plant Health inspection Service (APHIS) visited the site on Tuesday. They did confirm the presence of a similar wood-boring pest but could not visually confirm the emerald ash borer was present. The APHIS representative took a sample from the infected tree and sent it to an emerald ash borer specialist at the USDA's Systematic Entomology laboratory in Washington D.C. Wednesday the DNR received the lab results that confirmed the presence of the emerald ash borer. Photo above: James W. Smith Galleries exposed and sprouting at the base due to decline and death of the upper portion of the tree.

Photo below: David Roberts,

Waltz also suggests steps that Hoosiers should take to help retard the spread of the emerald ash borer to Indiana. "First, do not bring into Indiana firewood from Michigan or Ohio, particularly if the bark is still attached. In general, it is best to debark all firewood if you're traveling and be sure to burn all the wood you brought with you. Under federal quarantine, it is illegal to transport firewood from infested areas to any site outside the quarantined area."

MSU - The galleries up-close

Finally, Waltz suggested homeowners can help by keeping their trees well watered and watch out for signs of this pest. "The emerald ash borer first attacks weak and troubled trees. Ash trees need an inch of water per week to remain healthy. It's important to maintain tree vigor," he said. Additional information about the emerald ash borer is available on the DNR Web site at: Photos courtesy of United States Department of Agriculture, Forest Service web site:

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Need a “small” Tree? - continued from page 1 Don’t be alarmed if the common name “Rowan” tree is unfamiliar to you. In the United States this group of trees is more commonly referred to as mountain ash and sometimes whitebeam (Sorbus aria). Worlwide there are approximately 100 species in this genus thriving in the cooler northern regions. American Mountain ash (Sorbus americana) and showy mountain ash (Sorbus decora) are the more common species of the four species native to North America. The common name “Rowan” traveled with the early Europeans and is more appropriately reserved for Sorbus aucuparia, the European mountain ash. Add Korean mountain ash (Sorbus alnifolia) to the three already mentioned and that begins to cover the species provided in the nursery trade. But, a quick look at

Above: Leaf of Sorbus aucuparia

nursery catalogs and in outlets reveals several selections showcasing a variety of forms from columnar to oval that display subtle leaf, flower and fruiting variations. Michael Dirr’s “Manual of Woody Landscape Plants” lists 8 species with the majority of the nursery trade cultivars attributed to Sorbus aucuparia. For the remainder of this discussion I will focus on the more common American species American mountain ash (Sorbus americana) and showy mountain ash (Sorbus decora). These trees tend to be on the smaller side, 15-30 feet tall with a 12 foot canopy diameter. Thus, this tree can be a good choice for small yards and areas requiring a small tree. April bud break above and fruits

People are drawn to these trees due to several unusual characteristics. We’ll start

persisting through the winter

at the interior of the tree – the bark on the trunk is smooth (occasionally scaly)


and grayish-brown with significant lenticels. The form created by slender, spreading branches tends to be oval. Another significant feature is the foliage. The alternate, compound leaves tend to be 6-9 inches long with an odd number (11-17) of finely toothed leaflets. Unlike Sorbus aucuparia the serrations on the leaf margin almost completey encompass the leaf. Fall color, while not spectacular, can be a fantastic addition to a landscape. The fall colors range from yellow, yellow gold to reddish purple. But, what can really set off the fall color is the presence of the sometimes persistent bronze fruit. The fruit of the mountain ash is a pome or apple like and it is sustenance to a

Photos: Dave Hanson

Contact Phone Numbers

TCAAG Members:

Program Contacts:

Bob Condon – 952-890-1228

Mimi Hottinger – 507-388-4838

Gary Johnson – 612-625-3765 or Dave Hanson – 612-624-1226 or Mailing Address: 115 Green Hall, 1530 Cleveland Ave. North, St. Paul, MN 55108

Paula Denman – 612-338-1871

Lisa McDonald - 612-721-2672,

Laurie Drolson – 651-464-9829

Betsy McDonough - 651-779-0437

Bruce Granos – 952-423-5211,

Lu Schmidtke - 651-455-6125

Contacts: Regional Extension Educators: Bob Mugaas – 651-480-7706 Patrick Weicherding, – 763-767-3836 or Gary Wyatt, 507-389-8325 or County Contacts: Carver County (Jackie Smith) - (952) 442-4496 or Dakota County (Barb Stendahl) – 952-463-8002 or Olmstead County – 507-285-8250 Ramsey County – 651-777-8156 Scott County (Jackie Smith) - (952) 492-5410 or St. Louis County (Bob Olen) – 218-726-7512

Additional Reference Contacts: Debby Newman (Info-U) – 612-624-3263 Don Mueller, DNR Forestry – 651-772-6148 Ken Holman, DNR Forestry – 651-296-9110 Paul Walvatne MNDOT – 651-284-3793 Great River Greening – 651-665-9500 Tree Trust – 651-644-5800

Need a “small” Tree? - number of bird species. Yet, if you can beat the cedar waxwings, ruffed grouse, continued European starlings, robins, common grackles and the pine grosbeaks you might be

able to produce a treat for your morning toast. Dirr indicates that S. aucuparia fruit is made into an alcoholic beverage, a juice, vinegar, stewed, made into a tea and is used medicinally. The species do differ significantly in the color of the fruit that is produced and it can be diagnostic for identification purposes. While American mountain ash fruit is orangey-bronze, showy mountain ash fruit tends to be red. However, the characteristic that will really catch your attention occurs in early spring. The 1/3 inch, white flowers, especially on showy mountain ash, occur in flat topped clusters roughly 3-5 inches across that can be very abundant. When flowering is heavy against the dark green compound leaves, the trees can be spectacular. So, why doesn’t every one plant one of these beauties? You might say there is an Achilles heel or several! The trees tend to be poorly branched with tight branch angles that are susceptible to storm damage. Mountain ashes prefer cool environments and in warmer urban environments are susceptible to cankers, leaf rusts, crown gall, scab, leafhoppers, and several other insects. One of the big problems for this species is fireblight. It hits the species hard. All in all, bringing this “cool climate” species into the urban setting predisposes them to a batch of problems that tends to reduce them to a short-lived landscape specimen. If you have a good location and can keep the tree healthy – I for one would vote to give mountain ash a try!


Volume 11 Number 2DaveHansonandGaryJohnson,ManagingEditors Why? Pruning Trees By Dave Hanson 11 Putting Down Roots: By Cliff Johnson 3 Pleas...